Reading mask ROMs on ROM burner?
mike knudsen
(not EPROM) ROMs on a professional ROM burner?
Specifically, these are Motorola SCM-series chips,
8K x 8 bits, with 24 pins.
I have some MCM-68766 24-pin EPROMS that are supposed to
be compatible with the above, in that the EPROMs can be
plugged into the mask-ROM's sockets in the computer
and will work. A single pin on these EPROMs is used as
CE* (chip/read enable) during usage, but is pulsed to
a high voltage when being programmed.
Supposedly that same pin is just CE* in the mask ROMs.
What's weird is that our Data I/O ROM blower with its
Uni-Pak II, when set up to read/write the above EPROMs
(family/pin 25,29), won't read the mask ROMs -- it
gets Hex 44 in all locations. Anybody know what to do?
The mask ROMs are Radio Shack DOS for my Color Computer--
I want to patch some bytes in them to improve the disk
step rates. People read these ROMs fine on little
home ROM burners -- why can't the industrial-strength
units do it? Thanks, mike k
--
Mike J Knudsen ...ihnp4!ihwpt!knudsen
Bell Labs (AT&T) (312)-979-4132 (work)
Nobody pays for my opinions, which are mine alone.
"A mind is a terrible thing to waste, but the pay is good."
Cary Mednick
>Does anyone have any hints for reading mask-programmed
>(not EPROM) ROMs on a professional ROM burner?
There are two common problems that may occur. The first you have dealt
with by determining how the chip selects on the masked roms are programmed.
The second problem is that many masked roms are dynamic devices. That means
that the Chip Select line must toggle for the rom to function properly. The
best way that I have found to read a masked rom is through a target system
with an emulator. Store the file on disk and then send it to the Data I/O
programmer. I have an old Z80 board with a highly configurable Memory site
on it. I set up the chip selects and read away. Be sure that the hardware
toggles the Chip Enable, as many designs do not.
Please excuse me if the format of this is awkard, as this is my first response.
Cary Mednick ...ihnp4!chinet!cmm